1. Field of the Invention
The present invention relates to a gas supplying apparatus of a semiconductor fabrication system and to a method of testing the same. More particularly, the present invention relates to the testing of an injection valve of a gas supplying apparatus of the system for clogs.
2. Description of the Related Art
A plurality of gases are used to fabricate semiconductor devices, particularly in a chemical vapor deposition (CVD) process. For example, reactive gases such as Tetra-Ethyl-Ortho Silicate (TEOS), Tri-Ethyl-Phosphorus (TEPO) and Tri-Ethyl-Boron (TEB) are used and supplied into a process chamber of a CVD apparatus to form a planarization layer such as Boron-Phosphorus-Silicate Glass (BPSG) or a Phosphorus-Silicate Glass (PSG) layer. The reactive gases, namely the TEOS, TEPO and TEB, are supplied to the process chamber using a gas supplying apparatus which is installed at an external part of the chamber.
A conventional gas supplying apparatus includes a carrier gas supplying device for applying pressure to the reactive gases using a carrier gas such as N2, H2, and three injection valves connected in series to each other for gasifying liquid phases of the reactive gases and supplying the same to the process chamber. The gasified reactive gases are then supplied to the process chamber after being mixed with each other.
In this apparatus, the injection valve associated with the TEPO is typically the last in the series of the injection valves, and tends to become clogged from time to time. Such clogging was deemed to occur due to chemical characteristics of the TEPO or due to a reaction among the reactive gases. In the latter case, a reaction occurs because the injection valves are connected in series, whereby the reactive gases are mixed with each other before being introduced into the process chamber.
A study for solving the problem of injection valve clogging is disclosed in Korean Utility Model Laid-Open Publication No. 1999-0041454. In the study, each of injection valves was connected in parallel and a Mass Flow Controller (MFC) was installed in each of the valve lines.
However, injection valve clogging is still observed in the modified apparatus disclosed in the Korean Utility Model Laid-Open Publication No. 1999-004145. Therefore, it is assumed that the clogging is caused by the chemical characteristics of the TEPO rather than a reaction among the reactive gases.
In the modified apparatus, the reactive gases are provided into the reaction chamber at a predetermined ratio by the mass flower meters and liquid flow meters. However, the reaction gases are supplied into the process chamber at an incorrect concentration ratio if at least one injection valve is clogged. Obviously, then, a desired layer can not be formed when one or more of the injection valves is clogged.
It is therefore an object of the present invention to provide a semiconductor device fabrication system whose reactive gas supplying device(s) can be tested for clogs before the reactive gas(es) is/are supplied into the process chamber. Likewise, it is an object of the present invention to provide a method of testing a reactive gas supplying device(s) of a gas supplying apparatus for clogs.
It is another object of the present invention to provide a gas supplying apparatus having a reactive gas supplying device whose gas injection valve can be tested for clogs. Likewise, it is an object of the present invention to provide a method of testing a gas injection valve for clogs.
A gas supplying apparatus of the present invention includes a carrier gas supplying device for supplying a carrier gas under a predetermined pressure, at least one reactive gas supplying device connected in parallel to each other, and a pressure detecting device installed between the carrier gas supplying device and each reactive gas supplying device for detecting the pressure of the carrier gas as it enters a reactive gas supplying device, The pressure detecing device preferably is a mass flow meter. However, the pressure detecting device can be a pressure guage. The reactive gas(es) supplied from the reactive gas supplying device(s) are introduced into a process chamber in which a wafer is situated to produce a desired layer on the wafer.
When the gas supplying apparatus includes a plurality of reactive gas supplying devices, a respective switching valve is disposed between the pressure detecting device and each reactive gas supplying device. Each reactive gas supplying device may include a source of reactive gas in its liquid phase, and an injection valve for adjusting flow rate of the reactive gas and gasifying the reactive gas. Preferrably, the reactive gas supplying devices include a TEOS gas supplying device, a TEB gas supplying device, and a TEPO gas supplying device.
The carrier gas is supplied under a predetermined pressure from the carrier gas supplying device to a reactive gas supplying device. The pressure of the carrier gas adjacent an inlet of the reactive gas supplying device is detected by the pressure detecting device. The pressure of the carrier gas detected adjacent the inlet of the reactive gas supplying device is then compared to a first pressure corresponding to the pressure (detected or predetermined) under which the carrier gas is flowing from the carrier gas supplying device.
In the case of a plurality of reactive gas supplying devices, a reactive gas supplying device to be tested is rendered operational while the other reactive gas supplying device(s) is/are shut down. In particular, the switching valve associated with the reactive gas supplying device to be tested is in an ON position, thereby allowing carrier gas from the carrier gas supply device to flow thereto. On the other hand, the switching valve(s) associated with the other reactive gas supplying device(s) is/are in the OFF position.
Comparing the first pressure of the carrier gas detected or otherwise determined at the side of the carrier gas supplying device (adjacent the outlet thereof) with the second pressure of the carrier gas detected at at the side of the reactive gas supplying device (adjacent the inlet of the gas injection valve) yields an indication of whether the reactive gas supplying device being tested is clogged. In operating the semiconductor fabrication system, the reactive gas entrained by the carrier gas is allowed to flow into the process chamber to process the wafer only when the first detected pressure is equal to or less than the second pressure.